The present invention relates to an engine system and a control method for the engine system.
Engine systems include a blow-by gas recirculating device for recirculating blow-by gas, which is fuel gas leaking from the combustion chamber of an internal combustion engine into the crankcase. The blow-by gas recirculating device has a blow-by gas passage through which the intake passage and the crankcase communicate with each other. The blow-by gas recirculating device recirculates blow-by gas by discharging the blow-by gas from the crankcase into the intake passage via the blow-by gas passage.
For example, an engine system disclosed in Japanese Laid-Open Patent Publication No. 2013-124544 includes a blow-by gas recirculating device and a forced-induction device including a compressor arranged in an intake passage. The engine system also includes an ejector device. The ejector device discharges blow-by gas into the intake passage using intake air pressure raised through operation of the compressor, which is boost pressure.
The ejector device includes a drive gas passage and an ejector. The drive gas passage is connected to the intake passage in a manner bypassing the compressor. The ejector is arranged in the drive gas passage. The ejector communicates with the crankcase. As the compressor is operated through operation of the engine, the boost pressure is raised to cause air to flow in the drive gas passage and the ejector. Such airflow draws blow-by gas from the crankcase into the ejector. After having been drawn into the ejector, the blow-by gas passes through the drive gas passage and is then introduced into the intake passage, together with the air.
Since the blow-by gas is produced in the engine in a heated state, the blow-by gas is heated. In contrast, the air drawn into the intake passage is comparatively cold.
Accordingly, if the compressor is operated through operation of the engine in a significantly low-temperature environment, cold intake air flows into the ejector via the drive gas passage and thus cools the interior of the ejector. The blow-by gas, which is in a heated state, is drawn into the ejector, which is in a cold state. This rapidly cools the blow-by gas in the drive gas passage and in the ejector. Water contained in the blow-by gas is thus condensed to produce condensate water. The condensate water may freeze.
Once the condensed water freezes, the drive gas passage and the ejector become partially or entirely clogged. This decreases the flow amount of the air and blow-by gas, thus hampering appropriate recirculation of the blow-by gas.